Timeline: Sokol's Role in Berkshire's Lubrizol Deal

Warren Buffett's leading heir apparent at Berkshire Hathaway, David Sokol, has resigned after buying shares in Lubrizol Corp, a chemical company he then pushed Buffett to acquire.

Below is a timeline of events running up to the $9 billion deal and Sokol's resignation, based on Buffett's statement on Wednesday and Lubrizol's regulatory filing on March 25.

Fall 2010: Sokol requests Citigroup investment bankers to come up with a list of possible targets for Berkshire Hathaway, including in the chemical industry. Citi gives him a list of 18 companies, including Lubrizol.

Dec 13, 2010: Sokol discusses the list with Citi and says Lubrizol was the only company he found interesting. He asks a Citi representative to tell Lubrizol Chief Executive James Hambrick that Sokol was interested in meeting to discuss a possible deal.

Dec 14: Sokol buys 2,300 Lubrizol shares.

Dec 17: Citi relayed Sokol's interest to Hambrick, who said he would inform the Lubrizol board of Berkshire's interest.

Dec 21: Sokol sells the Lubrizol shares.

Jan 5-7, 2011: Sokol buys 96,060 Lubrizol shares after placing a 100,000-share order with a $104 per share limit price.

Jan 10: Lubrizol board convenes with Jones Day and Evercore to discuss a potential Berkshire deal. The board instructs CEO Hambrick to meet with Sokol

Jan 14: Sokol and Hambrick have a general talk over the phone and set up a meeting for Jan. 25

Jan 14 or 15: Sokol suggests buying Lubrizol to Buffett, with a "passing remark" that he owned some stock in the company. Buffett is not interested.

Jan 24: Buffett sends Sokol a short note expressing skepticism about making an offer for Lubrizol and preference to make another substantial acquisition.

Jan 25: Lubrizol CEO Hambrick meets with Sokol and gives him information about the chemical company, including internal forecasts for 2014 and 2015; Sokol reports the meeting to Buffett, who then warmed to the acquisition.

Jan 28: Evercore tell Lubrizol's board that Buffett called them the day before and expressed interest in the deal.

March 14: Berkshire announces plan to buy Lubrizol for $135 per share.

March 19: Shortly before leaving for a trip to Asia, Buffett learns the details of Sokol's purchase of Lubrizol shares.

March 28: Sokol's assistant delivers his letter of resignation to Buffett. Buffett says he had not asked for Sokol's resignation and that it came as a surprise. Sokol's letter says "it is my goal to utilize the time remaining in my career to invest my family`s resources in such a way as to create enduring equity value and hopefully an enterprise which will provide opportunity for my descendents and funding for my philanthropic interests."

March 30: Buffett announces Sokol's resignation request. He says, "Neither Dave nor I feel his Lubrizol purchases were in any way unlawful. He has told me that they were not a factor in his decision to resign."